Cell substratum modulates responses of preosteoblasts to retinoic acid

The aim of this study was to determine the role of ECM components of bone in regulating the differentiation and function of cells of the osteoblast lineage. Rat UMR 201 cells, phenotypically preosteoblast, were plated onto plastic tissue culture dishes or dishes coated with gelled type I collagen or reconstituted basement membrane (matrigel). Acute cell attachment assays showed that cells adhered to substrates in the following order: collagen > matrigel ? plastic. Proliferation rate up to 96 hr were similar on each substrate. However, if cells were treated with 10^?6 M retinoic acid (RA), proliferation rates were reduced compared with control for cells grown on collagen and matrigel but not on plastic. Morphological changes were matrix-specific; in subconfluent cultures, long thin processes were seen with cells grown on collagen and a pattern of interconnecting cell processes formed when cells were plated on matrigel. Striking differences were observed in the constitutive or RA-induced gene expression of cells grown on the different substrates. When cells plated on collagen were treated with RA, induction of mRNA for alkaline phosphatase (ALP) as well as ALP enzyme activity were much less than with cells grown on plastic. In contrast, RA treatment induced osteopontin (OP) mRNA expression more strongly in cells plated on collagen compared with plastic within 24 hr and this was maintained for 72 hr. RA treatment produced a two fold increase of pro-α 1(I) collagen mRNA in cells grown on plastic and matrigel but not in cells grown on collagen. Growth on collagen produced changes in the way UMR 201 cells responded to RA from which they did not fully recover in subsequent 48-hr growth periods on plastic. These results indicate that ECM components regulate the function of and are capable of modulating RA-induced differentiation of preosteoblasts. © 1993 Wiley-Liss, Inc.     

Differential expression and biological activity of retinoic acid–induced TGFβ isoforms in embryonic palate mesenchymal cells

The effect of retinoic acid (RA) on TGF-β mRNA expression and protein production in murine embryonic palate mesenchymal (MEPM) cells was examined by Northern blotting and TGF-β bioassay in association with TGF-β isoform-specific neutralizing antibodies. Heat or acid activation was used to distinguish between latent and active TGF-β protein released into the culture medium. RA had little or no effect on TGF-β1 mRNA expression and protein production. In contrast, RA increased TGF-β2 and β3 protein released into the culture medium, the protein being mostly in an inactive or latent form. The amount of active TGF-β released was increased relative to the total increase in TGF-β released, suggesting that RA treatment stimulated activation of latent TGF-β. RA also increased TGF-β2 mRNA expression; we have previously shown that RA upregulates TGF-β3 mRNA in these cells. RA and TGF-β individually inhibited ³H-thymidine incorporation into MEPM cell DNA, while, when administered simultaneously, they inhibited proliferative activity to a greater extent. Heat- or acid-activated conditioned medium (CM) from MEPM cells treated with RA was able to inhibit ³H-thymidine incorporation into MEPM cell DNA to an extent greater than seen with RA treatment alone. Coincubation of heat-activated CM from RA-treated MEPM cells with pan-specific or TGF-β2 or β3-specific neutralizing antibodies partially relieved the inhibitory effect on ³H-thymidine incorporation, suggesting that this proliferative response was due to RA-induced TGF-β. Simultaneous treatment with RA and TGF-β also stimulated gycosaminoglycan (GAG) synthesis to an extent greater than that seen with TGF-β treatment alone, this despite the ability of RA to inhibit GAG synthesis. These data demonstrate a role for RA and RA-induced TGF-β in the regulation of palate cell proliferation and GAG synthesis and suggest a role for TGF-β in retinoid-induced cleft palate. J. Cell. Physiol. 177:36–46, 1998. © 1998 Wiley-Liss, Inc.     

TGF-β 1 对人蜕膜基质细胞中趋化因子及其受体表达的影响

为探讨转化生长因子β1(TGF-β1)在蜕膜基质细胞中发挥免疫调节作用的机制,本研究以人妊娠初期的蜕膜基质细胞为研究对象,经0 ng/ml、1 ng/ml、5 ng/ml和10 ng/ml的TGF-β1处理后,运用RT-PCR方法检测趋化因子mRNA的表达,Western-blot检测趋化因子蛋白质的表达。结果表明:在mRNA水平和蛋白水平,高浓度的TGF-β1能够显著的下调蜕膜基质细胞中趋化因子配体CX3CL1、CXCL12和CXCL16的表达,有意义的上调趋化因子受体CXCR4和CXCR6的表达。研究结果提示,TGF-β1对趋化因子配体/受体有显著的调节作用,并通过趋化因子参与母胎界面的免疫调节。     

TGF-β1 induces the expression of type I collagen and SPARC,and enhances contraction of collagen gels,by fibroblasts from young and aged donors

Fibroblasts have a major role in the synthesis and reorganization of extracellular matrix that occur during wound repair. An impaired biosynthetic or functional response of these cells to stimulation by growth factors might contribute to the delayed wound healing noted in aging. We, therefore, compared the responses of dermal fibroblasts from young and elderly individuals (26, 29, 65, 89, 90, and 92 years of age) to transforming growth factor-β1 (TGF-β1) with respect to: (1) the synthesis of type I collagen and SPARC (two extracellular matrix proteins that are highly expressed by dermal fibroblasts during the remodeling phase of wound repair) and (2) the contraction of collagen gels, an in vitro assay of wound contraction. With the exception of one young donor, all cultures exposed for 44 hours to 10 ng/ml TGF-β1 exhibited a 1.6- to 5.5-fold increase in the levels of secreted type 1 collagen and SPARC, relative to untreated cultures, and exhibited a 2.0- to 6.2-fold increase in the amounts of the corresponding mRNAs. Moreover, the dose-response to TGF-β1 (0.1–10 ng/ml), as determined by synthesis of type I collagen and SPARC mRNA, was as vigorous in cells from aged donors as in cells from a young donor. In assays of collagen gel contraction, fibroblasts from all donors were stimulated to a similar degree by 10 ng/ml TGF-β1. In conclusion, cells from both young and aged donors exhibited similar biosynthetic and contractile properties with exposure to TGF-β1. It therefore appears that the impaired wound healing noted in the aged does not result from a failure of their dermal fibroblasts to respond to this cytokine. © 1994 Wiley-Liss, Inc.     

1,25-Dihydroxyvitamin D3 stimulates the synthesis of matrix gamma-carboxyglutamic acid protein by osteosarcoma cells. Mutually exclusive expression of vitamin K-dependent bone proteins by clonal osteoblastic cell lines

Several clonal rat osteosarcoma cell lines were tested for the ability to express and secrete matrix Gla protein (MGP), a small vitamin K-dependent protein found in bone and cartilage. Two independently derived cell lines, UMR 106-01 and ROS 25/1, expressed MGP mRNA and secreted MGP antigen identical in size with that found in bone. No MGP message could be detected in ROS 17/2 and 2/3 cells, cell lines previously shown to synthesize the other known vitamin K-dependent bone protein, bone Gla protein (BGP), and no BGP mRNA could be detected in the cell lines which synthesize MGP. Since UMR 106-01 and ROS 17/2 are presently the best characterized clonal osteoblastic cell lines, the discovery of the mutually exclusive expression of MGP and BGP by these cell lines indicates that osteosarcoma cells can be fixed in different phenotypic states and that MGP and BGP should be useful markers for the analysis of phenotypic expression in bone. Treatment of UMR 106-01 cells with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) dramatically increased MGP mRNA within 4 h and, by 24 h, increased MGP secretion 15-fold. This is only the second example of a bone matrix protein whose synthesis is dramatically increased by vitamin D, the first being the 6-fold stimulation of BGP synthesis by 1,25(OH)2D3 in ROS 17/2 cells. The discovery that MGP and BGP are similarily regulated by 1,25(OH)2D3 was unexpected since the two proteins differ markedly in structure, physical properties, and tissue distribution. Since the synthesis of MGP is rapidly and dramatically increased by 1,25(OH)2D3, it is probable that MGP plays a role in the normal bone response to the hormone. MGP may also be the vitamin K-dependent protein whose abnormal synthesis in the Warfarin-treated animal modifies the bone response to 1,25(OH)2D3.     

Synergistic Action of Transforming Growth Factor-β and Insulin-like Growth Factor-I Induces Expression of Type II Collagen and Aggrecan Genes in Adult Human Articular Chondrocytes

Reexpression of aggrecan and type II collagen genes in dedifferentiated adult human articular chondrocytes (AHAC) in suspension culture varied widely depending on the specific lot of bovine serum used to supplement the culture medium. Some lots of serum provided strong induction of aggrecan and type II collagen expression by AHAC while others did not stimulate significant production of these hyaline cartilage extracellular matrix molecules even following several weeks in culture. Addition of 50 ng/ml insulin-like growth factor-I (IGF-I) to a deficient serum lot significantly enhanced its ability to induce aggrecan and type II collagen mRNA. Given this observation, IGF-I and other growth factors were tested in defined serum-free media for their effects on the expression of these genes. Neither IGF-I nor insulin nor transforming growth factor β (TGF-β) alone stimulated induction of aggrecan or type II collagen production by dedifferentiated AHAC. However, TGF-β1 or TGF-β2 combined with IGF-I or insulin provided a strong induction as demonstrated by RNase protection and immunohistochemical assays. Interestingly, type I collagen, previously shown to be downregulated in serum supplemented suspension cultures of articular chondrocytes, persisted for up to 12 weeks in AHAC cultured in defined medium supplemented with TGF-β and IGF-I.     

The role of thrombospondin-1-mediated TGF-��1 on collagen type III synthesis induced by high glucose

Transforming growth factor-β1 (TGF-β1) has been thought to play a major role during cardiac fibrosis in the development of diabetic cardiomyopathy, and cardiac fibrosis mainly as a result of an increase of collagen type III occurs in the human hearts with diabetes. Thrombospondin-1 (TSP-1) has been reported to activate the latent complex of TGF-β1. We examined the effects of TSP-1 on the expression of TGF-β1 and collagen type III by rat cardiac fibroblasts in high ambient glucose. We demonstrated that high glucose induces the mRNA and protein expression of collagen type III, TGF-β1, and TSP-1. Furthermore, the mRNA and protein expression of collagen type III induced by high glucose was downregulated after treatment with TGF-β1 antibody, or TSP-1 siRNA. The expression of TGF-β1 increased by high glucose was also reversed after treatment with TSP-1 siRNA. Our findings suggest that the TSP-1 participates in the upregulation of TGF-β1, collagen type III by high glucose and may provide new therapeutic strategies for diabetic cardiomyopathy.     

Phenotypic consequences of transforming growth factor β1 gene ablation in murine embryonic fibroblasts: Autocrine control of cell proliferation and extracellular matrix biosynthesis

The profound effects of transforming growth factor β1 (TGF-β1) on the immune system, cardiogenesis, in yolk sac hematopoeisis and in differentiation of endothelium have been demonstrated by detailed analyses of TGF-β1 knockout mice during embryogenesis. We have systematically examined the autocrine and paracrine roles of TGF-β1 in cell proliferation and in its ability to modulate the gene expression of selected components of extracellular matrix (ECM) using embryonic fibroblasts from TGF-β1 null mice (TGF-β1^−/−). The rates of cell proliferation of embryonic fibroblasts from normal mice (TGF-β1^+/+) and TGF-β1 null mice were compared by cell counting, by ³H thymidine incorporation, and by measuring the fraction of cells in the G1, S, and G2/M phases of the cell cycle by fluorescent activated cell sorting (FACS). Concurrently, the expression of pro-α1(I) collagen, fibronectin, and plasminogen activator inhibitor-1 (PAI-1) was also quantified by hybridization of total mRNA from TGF-β1^+/+ and TGF-β1^−/− embryonic fibroblasts. We report that TGF-β1^−/− cells proliferated at about twice the rate of TGF-β1^+/+ cells. Further, TGF-β1 null fibroblasts accumulated and synthesized lower constitutive levels of pro-α1(I) collagen, fibronectin, and PAI-1 mRNA. The quantitative differences in the rates of cell proliferation and ECM gene expression between TGF-β1^+/+ and TGF-β1^−/− cells could be eliminated by treatment of TGF-β1^+/+ cells with a neutralizing antibody of TGF-β1. Thus, our results are consistent with the hypothesis that TGF-β1 acts as a negative autocrine regulator of growth and a positive autocrine regulator of ECM biosynthesis in embryonic fibroblasts. 176:67–75, 1998. Published 1998 Wiley-Liss, Inc.

1 This article was prepared by a group of United States government employees and non-United States government employees, and as such is subject to 17 U.S.C. Sec. 105.

     

The naïve effector cells of collagen type I during acute experimental pancreatitis are acinar cells and not pancreatic stellate cells

Objective

The purpose of this study was to investigate the expression of collagen type I and the mRNA level of its regulatory factor, TGF-β1, in tissue samples of acute pancreatitis and to determine the significance of collagen type I in predisposition to pancreatic fibrosis during acute pancreatitis.

Methods

Sprague–Dawley rats were divided into an experimental group (30 rats) and a control group (12 rats). The rats in the experimental group were intraperitoneally injected with cerulein to induce acute pancreatitis. The distribution and expression of collagen type I in the pancreatic tissues were examined by immunohistochemical staining. The mRNA level of TGF-β1 was determined by real-time polymerase chain reaction (PCR).

Results

(1) Collagen type I was localized in the cytoplasm of pancreatic acinar cells. With pancreatitis progressed, strong positive staining for collagen type I covered whole pancreatic lobules, whereas, the islet tissue, interlobular area, and pancreatic necrotic area were negative for collagen type I. (2) The level of TGF-β1 mRNA in rats from the experimental group increased gradually the establishment of acute pancreatitis, and was significantly higher than that in the control group at every time point.

Conclusions

(1) During acute pancreatitis, pancreatic acinar cells, not pancreatic stellate cells as traditionally believed, were the naïve effector cells of collagen type I. (2) TGF-β1 played a key role in regulating collagen I expression during acute pancreatitis.     

Induction of cardiac fibroblast lysyl oxidase by TGF-β1 requires PI3K/Akt, Smad3, and MAPK signaling

Lysyl oxidase (LOX) is a key extracellular enzyme responsible for the post-translational modification of collagens I and III to form mature fibrillar collagen. Increased expression of LOX is associated with fibrosis and cardiac dysfunction, yet little is known about the regulation of LOX in the heart. In this study, the cell signaling pathways responsible for the regulation of LOX expression by transforming growth factor (TGF)-β1 were assessed. Adult cardiac fibroblasts were isolated from male Sprague-Dawley rat hearts by enzymatic digestion. Fibroblasts were grown in DMEM with 10% FBS until approximately 80% confluent, growth arrested for 24h, and then treated with TGF-β1 (0-10 ng/ml), in the absence or presence of inhibitors of (1) PI3K (wortmannin), (2) Smad3 (SIS3), (3) p38-MAPK (PD169316), (4) JNK (SP600125) and (5) ERK1/2 (PD98059). TGF-β1 treatment significantly upregulated LOX mRNA and protein expression in cardiac fibroblasts, as well as activity in the cell-conditioned media. Concomitant increases in collagen types I and III, and bone morphogenic protein (BMP-1) expression were found in response to TGF-β1. The increase of LOX protein in response to TGF-β1 was prevented by inhibitors of PI3K, Smad3, p38-MAPK, JNK and ERK1/2. Blockade of PI3K also decreased TGF-β1 induced phosphorylation of Smad3, suggesting that the PI3K/Akt and Smad pathways may be integrated in TGF-β1 signaling. Further studies are warranted to address the regulation of LOX in the normal and diseased heart, and how this critical extracellular enzyme may be targeted for clinical benefit.     

TGF-β1和FBRS可指示肝纤维化发展程度

为了探讨转化生长因子(TGF-β1)、外周血纤维化蛋白(FBRS)表达水平变化与肝纤维化发生发展的相关性,本研究选取自2015年5月至2017年6月间在我院诊治的慢性病毒性肝炎患者120例,设为肝炎组。采用免疫组化法检测肝组织TGF-β1的表达水平,酶联免疫分析检测血清中TGF-β1的含量,RT-PCR检测外周血单个核细胞FBRS mRNA的表达水平,分析TGF-β1、FBRS与肝纤维化程度的相关性。研究结果表明:随肝纤维化程度的不同,肝组织TGF-β1、血清TGF-β1表达水平、FBRS mRNA表达水平与肝脏胶原含量同步性升高(p<0.05)。进一步的相关分析表明:肝组织TGF-β1水平、FBRS mRNA与肝纤4项检查,即血清Ⅲ型前胶原(PC-Ⅲ)、Ⅳ型胶原片段(Ⅳ-C)、层粘连蛋白(LN)和透明质酸(HA)水平之间均呈正相关。本研究结果初步得出结论,慢性病毒性肝炎肝组织TGF-β1、血清TGF-β1表达水平、外周血FBRS的表达水平与肝组织纤维化程度呈正相关。     

Alcohol-induced increase in BMP levels promotes fatty liver disease in male prediabetic stage Otsuka Long-Evans Tokushima Fatty rats

Alcohol consumption exacerbates liver abnormalities in animal models, but whether it increases the severity of liver disease in early diabetic or prediabetic rats is unclear. To investigate the molecular mechanisms underlying alcohol-induced liver steatosis or hepatitis, we used a prediabetic animal model. Otsuka Long-Evans Tokushima Fatty (OLETF) and Long-Evans Tokushima Fatty (LETO) rats were pair-fed with an ethanol-containing liquid diet for 6 weeks. Compared with controls, OLETF and LETO rats displayed more pronounced liver steatosis and higher plasma levels of serum glutamic oxaloacetic transaminase (SGOT) and serum glutamate pyruvate transaminase (SPGT), indicating liver injury. Ethanol-fed LETO (Pd-L-E) rats showed mild liver steatosis and no inflammation compared with ethanol-fed OLETF (Pd-O-E) rats. Although precursor and active SREBP-1 levels in the liver of ethanol-fed OLETF rats significantly increased compared with control diet-fed OLETF rats (Pd-O-C), those of Pd-L-E rats did not. Bone morphogenetic protein (BMP) and TGF-β1 balance in Pd-O-E rats was significantly altered because BMP signaling was upregulated by inducing BMP2, BMP4, BMP7, BMP9, Smad1, and Smad4, whereas TGF-β1, Smad3, and Erk were downregulated. Activation of TGF-β/Smad signaling inhibited BMP2 and BMP9 expression and increased epithelial-mesenchymal transition (EMT) marker levels (Hepcidin, Snail, and Twist) in the liver of LETO rats. Livers of ethanol-fed OLETF rats showed increased levels of vimentin, FSP-1, α-SMA, MMP1, MMP13, and collagen III compared with rats of other groups, whereas EMT marker levels did not change. Thus, BMP exerted anti- and/or pro-fibrotic effects in ethanol-fed rats. Therefore, BMP and TGF-β, two key members of the TGF-β superfamily, play important but diverse roles in liver steatosis in young LETO and OLETF rats.     

Retinoids potentiate transforming growth factor-β activity in bovine endothelial cells through up-regulating the expression of transforming growth factor-β receptors

Retinoic acid (RA) induces the activation of latent transforming growth factor-β (TGF-β) in bovine aortic endothelial cells (BAECs) via enhancement of cellular plasminogen activator (PA)/plasmin levels. The resultant TGF-β suppresses the excessive fibrinolytic activity by decreasing PA expression and stimulating expression of the PA inhibitor, PA inhibitor-1 (PAI-1), and inhibits cell proliferation. Here, we report that, in this regulatory system, RA simultaneously up-regulates the expression of TGF-β receptor types I and II, resulting in enhancement of TGF-β activity in the cells. RA increased the numbers of high- and low-affinity binding sites for ¹²⁵I-TGF-β1 2.1-fold and 1.5-fold, respectively, without alteration of their Kd values. Affinity labeling and Western and Northern blotting studies showed that, following RA treatment, surface levels of both type I and type II receptors increased due to augmentation in their mRNA levels. The effect was dose- and time-dependent. Treatment with 1 μM RA for 15 hr increased mRNA levels of type I and II receptor threefold and eightfold, respectively. Pretreatment of BAECs with either RA or retinol lowered the concentration of TGF-β1 required to suppress PA levels, to enhance PAI-1 levels, and to inhibit cell proliferation. Thus, retinoids may regulate cellular functions of BAECs not only by inducing the formation of active TGF-β but also by stimulating TGF-β receptor expression. This regulatory mechanism may sustain TGF-β-mediated regulation of EC function at a focal site where RA is acting. J. Cell. Physiol. 176:565–573, 1998. © 1998 Wiley-Liss, Inc.     

The antifibrotic effects of TGF-β1 siRNA on hepatic fibrosis in rats

Background/aims: Hepatic fibrosis results from the excessive secretion of matrix proteins by hepatic stellate cells (HSCs), which proliferate during fibrotic liver injury. Transforming growth factor (TGF)-β1 is the dominant stimulus for extracellular matrix (ECM) production by stellate cells. Our study was designed to investigate the antifibrotic effects of using short interference RNA (siRNA) to target TGF-β1 in hepatic fibrosis and its mechanism in rats exposed to a high-fat diet and carbon tetrachloride (CCL4). Methods: A total of 40 healthy, male SD (Sprague–Dawley) rats were randomly divided into five even groups containing of eight rats each: normal group, model group, TGF-β1 siRNA 0.125 mg/kg treatment group, TGF-β1 siRNA 0.25 mg/kg treatment group and TGF-β1 siRNA negative control group (0.25 mg/kg). CCL4 and a high-fat diet were used for 8 weeks to induce hepatic fibrosis. All the rats were then sacrificed to collect liver tissue samples. A portion of the liver samples were soaked in formalin for Hematoxylin–Eosin staining, classifying the degree of liver fibrosis, and detecting the expression of type I and III collagen and TGF-β1; the remaining liver samples were stored in liquid nitrogen to be used for detecting TGF-β1 by Western blotting and for measuring the mRNA expression of type I and III collagen and TGF-β1 by quantitative real-time polymerase chain reaction. Results: Comparing the TGF-β1 siRNA 0.25 mg/kg treatment group to the model group, the TGF-β1 siRNA negative control group and the TGF-β1 siRNA 0.125 mg/kg treatment group showed significantly reduced levels of pathological changes, protein expression and the mRNA expression of TGF-β1, type I collagen and type III collagen (P < 0.01). Conclusions: Using siRNA to target TGF-β1 can inhibit the expression of TGF-β1 and attenuate rat hepatic fibrosis induced by a high-fat diet and CCL4. A possible mechanism is through the down-regulation of TGF-β1 expression, which could inhibit HSC activation, as well as the proliferation and collagen production of collagen reducing, so that collagen deposition in the liver is reduced.     

Ⅱ型肺泡上皮细胞间质转分化中的Notch-1/ Twist-1信号通路机制*

目的:通过研究Notch-1/Twist-1信号通路参与Ⅱ型肺泡上皮细胞间质转分化(EMT)作用,为阐明肺纤维化(PF)发病机制提供理论依据。方法:动物实验设对照组和博莱霉素(BLM)组(n=15)。气管注射BLM(7 500 U/kg)诱导肺纤维化大鼠模型,造模后28 d取左肺下叶固定于10%福尔马林中,进行HE、Masson及转化生长因子-β1(TGF-β1)免疫组化染色。体外培养Ⅱ型肺泡上皮细胞(RLE-6TN),细胞实验设对照(Control)组、TGF-β1(5 ng/ml)组、TGF-β1+ Notch-1 siRNA阴性对照组(NC siRNA, 100 pmol/L)和TGF-β1+Notch-1 siRNA干扰组(Notch-1 siRNA, 100 pmol/L),每组设9个复孔。细胞先用NC siRNA或Notch-1 siRNA预处理24 h,再用TGF-β1处理48 h。检测肺组织和(或)II型肺泡上皮细胞内TGF-β1、I型胶原(collagen I)、III型胶原(collagen III)、E-钙粘蛋白(E-Cadherin)、紧密连接蛋白-1(ZO-1)、波形蛋白(Vimentin)、N-钙粘蛋白(N-Cadherin)、Notch-1、Notch-1胞内域(NICD)、Hes-1和Twist-1 mRNA和(或)蛋白表达。结果:动物实验结果显示,与对照组相比,BLM组肺泡萎缩、塌陷并发生融合,肺泡间隔明显增宽,可见大量炎性细胞的浸润。肺间质胶原纤维沉积明显增多,collagen I和collagen III的表达明显增加(P＜0.01);另外,肺BLM组织中E-cadherin和ZO-1表达明显下降而Vimentin和N-cadherin的表达明显增加(P＜0.01);同时,BLM组肺组织TGF-β1、Notch-1、NICD、Hes-1和Twist-1的表达也明显上调(P＜ 0.01)。细胞实验结果显示,与Control相比,TGF-β1组Notch-1、NICD、Hes-1、Twist-1、collagen I和collagen III的表达明显升高,同时E-Cadherin和ZO-1的表达明显降低而Vimentin和N-cadherin的表达明显升高(P＜0.01)。与TGF-β1组相比,Notch-1 siRNA能够明显降低TGF-β1诱导Notch-1、NICD、Hes-1和Twist-1的表达(P＜0.05或P＜ 0.01),同时E-Cadherin和ZO-1的表达明显升高而Vimentin和N-cadherin的表达明显降低(P＜0.05或P＜0.01)。另外Notch-1 siRNA还能够明显降低TGF-β1诱导的collagen I和collagen III的表达(P＜0.05或P＜0.01)。结论:Notch-1/Twist-1信号通路参与了Ⅱ型肺泡上皮细胞EMT,可能参与了肺纤维化的发生发展。     

BMP6 increases TGF-β1 production by up-regulating furin expression in human granulosa-lutein cells

Bone morphogenetic protein 6 (BMP6) and transforming growth factor-β1 (TGF-β1) are key intraovarian regulators that play essential roles in regulating mammalian follicular function and promoting oocyte maturation. Furin, a member of the subtilisin-like proprotein convertase family, promotes the activation of diverse functional proteins by cleaving protein precursors in the secretory pathway. The aim of this study was to investigate the effect and underlying molecular mechanisms by which BMP6 regulates the expression of furin to increase TGF-β1 production. Primary and immortalized (SVOG) human granulosa-lutein (hGL) cells were used as study models. Our results show that BMP6 significantly up-regulated the expression of furin and increased the production of TGF-β1 in hGL cells. Using dual inhibition approaches (kinase receptor inhibitors and small interfering RNA-targeted knockdown), we demonstrate that both activin receptor-like (ALK)2 and ALK3 are involved in the BMP6-induced up-regulation of furin. Additionally, knockdown of furin abolished BMP6-induced increases in TGF-β1 production. Moreover, knockdown of endogenous SMAD4 reversed the BMP6-induced increase in furin expression. These results indicate that the ALK2/3-mediated canonical SMAD signaling pathway is required for the stimulatory effect of BMP6 on furin expression, which in turn increases the production of TGF-β1 in hGL cells. Our findings provide insights into the molecular interactions and mechanisms of two intrafollicular growth factors in hGL cells.